I want to fix Physics in DnD

[Ephemeral_Being]

Okay. Granted, magic makes some of this an abstract concept. But I'm looking for something concrete. Something we can look at, and say "1d6 damage is equivalent to a force of X Newtons. Specifically, in the areas of:


Force Damage
Fixed Damage, covered by official published materials
Sonic Damage (which has an equivalent in real world terms)


NOT Fall Damage, though. Because the calculation for that is what I'm trying to fix. I want to homebrew a better, more accurate fall damage system than "1d6 per 10 feet." Take your character's mass in kg, the height of the wall, and see how much damage they take on impact. Because a Barbarian in plate mail shouldn't take the same damage as a Halfling in leather. That, and I want to theoretically calculate the amount of force exerted by "force damage" spells, to determine their effects on the world.

Does anyone know of something like that? Something from another d20 system, maybe?

[BowStreetRunner]

It's more than just mass and height however - drag comes into play when reaching terminal velocity (http://ffden-2.phys.uaf.edu/211.web.stuff/Kuhns/terminal_velocity.htm).

[Ephemeral_Being]

It's more than just mass and height however - drag comes into play when reaching terminal velocity (http://ffden-2.phys.uaf.edu/211.web.stuff/Kuhns/terminal_velocity.htm).

Yes, I am aware of that. The calculation is more complex than they teach you in a high school physics class. But I need a baseline to work off of, before I can convert any amount of force into damage.

[Snowbluff]

It's wrong to apply physics to the Force type in DnD. Just so wrong. It's like... ugh. You can't get more wrong than that.

[Jack_Simth]

NOT Fall Damage, though. Because the calculation for that is what I'm trying to fix. I want to homebrew a better, more accurate fall damage system than "1d6 per 10 feet." Take your character's mass in kg, the height of the wall, and see how much damage they take on impact. Because a Barbarian in plate mail shouldn't take the same damage as a Halfling in leather. That, and I want to theoretically calculate the amount of force exerted by "force damage" spells, to determine their effects on the world.
Oddly enough, impact energy of an object falling from rest (if you ignore air resistance, at least) is simply mass times gravity times height, a straight-up linear equation. Sure, the SPEED is not linear... but kinetic energy is mass times velocity squared, and it all works out.

That said: D&D breaks down when you attempt to do this sort of thing. You check ten different things and you'll get ten contradictory baselines. You also generally do not want your players thinking in terms of applying physics to D&D.

[Glorius Nippon]

So suddenly using the longest possible range archer build is plausible? If I remember it was gotten to 43.2ish miles. Considering a round is 6 seconds, and part of that round is used to draw and fire the bow, how fast is the arrow itself then moving? Now what if someone is shooting more than one arrow per round? Things to keep in mind when thinking about implementing physics into D&D.

[Deophaun]

Fixing physics in D&D:

Wizard mutters spell and throws piece of bat guano at you.
Punch wizard for getting bat guano on your clothes.

[atemu1234]

Well, then, I guess the first maths problem in D&D on the subject of physics will be, "What is the flight speed of a catgirl hurled at a brick wall?"

[Duke of Urrel]

It's wrong to apply physics to the Force type in DnD. Just so wrong. It's like... ugh. You can't get more wrong than that.


Oddly enough, impact energy of an object falling from rest (if you ignore air resistance, at least) is simply mass times gravity times height, a straight-up linear equation. Sure, the SPEED is not linear... but kinetic energy is mass times velocity squared, and it all works out.

That said: D&D breaks down when you attempt to do this sort of thing. You check ten different things and you'll get ten contradictory baselines. You also generally do not want your players thinking in terms of applying physics to D&D.

I agree with these comments, and I'll add a third. I think being too concerned about realistic physics puts characters that use less magic or no magic at all at a greater disadvantage compared to characters that use more magic. One of the salient features of magic is that it generally breaks the laws of physics.

Nearly all of us agree that mundane characters, played strictly according to the RAW, are already disadvantaged compared to magical ones. Imposing more realistic physics would only increase this disparity. I favor imagining mundane characters at high levels as having extraordinary powers that go far beyond the limits of real-world physics. This includes the ability to fall from great heights without dying, among many other super-human powers.

Another problem with applying real-world physics to D&D is that it rules out giant-sized creatures, particularly those that are supposed to be able to fly.

[Karl Aegis]

Can anyone give an example of one instance where anything has been given a definite mass in any printed book? From what I can tell gravity doesn't even work correctly.

[Curmudgeon]

Except for tripping, falling is fairly easy to fix: if you bump up the maximum to 50d6 for falling 500' you're getting to terminal velocity. Tripping someone inconveniences them, but does no harm.

The square-cube issue would make most creatures of Large+ size incapable of moving (or, most likely, breathing).

Perhaps the biggest problem in fixing physics in D&D is that the game has no acceleration or momentum. Characters go from a stop to their speed instantly, and even if they Run the whole round they're at a stop on their next turn. Missiles hit less often but don't do less damage with greater distance.

[Snowbluff]

The square-cube issue would make most creatures of Large+ size incapable of moving (or, most likely, breathing).


Um, would this actually be the case, considering how strong these creatures are? Or the fact that most of them aren't mundane animals?

[KrimsonNekros]

What don't you like the commoner railgun?

[Invader]

http://www.interbutt.org/plog-content/thumbs/sfwmaybe/general-coolfunny/large/1174-qar5n6mx7vgpiv4l42ut7snyw9.jpg

[Telok]

Perhaps the biggest problem in fixing physics in D&D is that the game has no acceleration or momentum. Characters go from a stop to their speed instantly, and even if they Run the whole round they're at a stop on their next turn. Missiles hit less often but don't do less damage with greater distance.

In our game this is one area that we call physics in. Ever since one of us hit a Dispel Magic trap while riding a... Phantom Steed spell? With beefed up CL that character was going over 90 mph.

I think we settled on 1d6 damage and 10' skid marks per 10 mph, and a tumble check DC equal to the mph to halve the damage unless you hit something before your skid stopped.

[Ephemeral_Being]

Except for tripping, falling is fairly easy to fix: if you bump up the maximum to 50d6 for falling 500' you're getting to terminal velocity. Tripping someone inconveniences them, but does no harm.

The square-cube issue would make most creatures of Large+ size incapable of moving (or, most likely, breathing).

Perhaps the biggest problem in fixing physics in D&D is that the game has no acceleration or momentum. Characters go from a stop to their speed instantly, and even if they Run the whole round they're at a stop on their next turn. Missiles hit less often but don't do less damage with greater distance.

So, everyone is against this plan?

Fine, fine. I'll let it go. I just thought that it would be interesting if there was a way to do it. I play with a bunch of engineers and physicists. They like "realism." So when someone trots out a book with 100 Exploding Runes spells cast on one page and reads it, they want to know if the resulting explosion is enough to cause the tower they're inside to collapse. And having math to back up your ruling is always good.

[Ashtagon]

I once tried to integrate the falling damage rules with impact speeds for car (or cart or flying, I suppose) crashes. After all, there's no conceptual difference between hitting something horizontally or hitting something vertically, right?

Let it go. You'll drive yourself insane trying.

[Curmudgeon]

Um, would this actually be the case, considering how strong these creatures are? Or the fact that most of them aren't mundane animals?
Some creatures might be strong enough to move their own mass. However, you need to take in oxygen proportional to that mass, which increases with the cube of the creature's length. Unfortunately, the working surface of your lungs only goes up as the square of that length. Not being able to breathe enough to support your metabolism means you don't get to live.

[PaucaTerrorem]

Aaaaaaaaaand god just killed a catgirl.

[Gray Mage]

So, everyone is against this plan?

Fine, fine. I'll let it go. I just thought that it would be interesting if there was a way to do it. I play with a bunch of engineers and physicists. They like "realism." So when someone trots out a book with 100 Exploding Runes spells cast on one page and reads it, they want to know if the resulting explosion is enough to cause the tower they're inside to collapse. And having math to back up your ruling is always good.

In this case you know the damage is done in HP (might be a pain to manually roll all that dice though) so you can apply it to the floor and nearby walls. As long as you know the materials and thikness, you can determine if they break or not.

[Amphetryon]

So, everyone is against this plan?

Fine, fine. I'll let it go. I just thought that it would be interesting if there was a way to do it. I play with a bunch of engineers and physicists. They like "realism." So when someone trots out a book with 100 Exploding Runes spells cast on one page and reads it, they want to know if the resulting explosion is enough to cause the tower they're inside to collapse. And having math to back up your ruling is always good.

Do they want to know the rate of cellular change that takes place (or alternate explanation) for Alter Self, Polymorph, etc. also, or just the explosion damage? Have you established the precise gravity, daylight, and size of the world in which they adventure - as that's likely to impact several areas of your equations?

What I'm asking here is, how much do you want to 'fix Physics in D&D,' and how much do you just want to determine if explosions can cause structural damage?

[atemu1234]

Aaaaaaaaaand god just killed a catgirl.

It's ok. I'm pretty sure they're already extinct.

[Larrx]

So, everyone is against this plan?

Fine, fine. I'll let it go. I just thought that it would be interesting if there was a way to do it. I play with a bunch of engineers and physicists. They like "realism." So when someone trots out a book with 100 Exploding Runes spells cast on one page and reads it, they want to know if the resulting explosion is enough to cause the tower they're inside to collapse. And having math to back up your ruling is always good.

The math for property damage already exists, walls and floors have hardness which varies by material and hitpoints that vary by thickness. There are tables in the DMG I think? As far as falling damage goes, I think even the simple high school mgh formula would be too cumbersome to use in actual play (I can't even remember any masses or weights listed any where, although I'm sure there are a few here and there, so you'd have to do a lot of work and guesstimating to implement this). A quick and dirty fix that I sometimes use is I raise or lower the damage cap by 4d6/size category. It's not perfect (physics wise), but it sorta accounts for the fact that more massive creatures should take more falling damage if you squint at it. And it's super easy to use, and doesn't slow down play.

Assigning a force/point of damage value just doesn't work in DnD. Remember, hit points are an abstraction. A character can have his skull cleaved in half by a great ax exactly once. The fact that higher level characters can take a crit from an orc and keep fighting (while a first level character would die) is not an attempt to model that the higher level dude has back-up heads. It's modeling the fact that s/he has the combat experience to avoid/deflect/lessen the blow. There simply isn't a relationship between force and hit point damage(except for the falling rules). If a maneuver or spell applies a force it models that by moving the target around the grid independent of how much damage (if any) it does.

[Jack_Simth]

The math for property damage already exists, walls and floors have hardness which varies by material and hitpoints that vary by thickness. There are tables in the DMG I think?For objects: Yep (http://www.d20srd.org/srd/exploration.htm#breakingAndEntering). For walls and doors: Also yep (http://www.d20srd.org/srd/epic/obstacles.htm).

[Rebel7284]

Some creatures might be strong enough to move their own mass. However, you need to take in oxygen proportional to that mass, which increases with the cube of the creature's length. Unfortunately, the working surface of your lungs only goes up as the square of that length. Not being able to breathe enough to support your metabolism means you don't get to live.

While as the size of the creature goes up, this is true eventually... have you guys heard of an elephant? How about an apatosaurus? You can get pretty large before you can no longer metabolize.

[Deophaun]

They like "realism." So when someone trots out a book with 100 Exploding Runes spells cast on one page and reads it, they want to know if the resulting explosion is enough to cause the tower they're inside to collapse. And having math to back up your ruling is always good.
As the rune explodes when you read it, destroying the page and thus the other 99 runes on it, what tower is taken down by 6d6 points of force damage?

[Ashtagon]

As the rune explodes when you read it, destroying the page and thus the other 99 runes on it, what tower is taken down by 6d6 points of force damage?

http://i867.photobucket.com/albums/ab238/tomasdiaz/Salsa/HuffPuff.jpg

[Coldsturm]

http://i867.photobucket.com/albums/ab238/tomasdiaz/Salsa/HuffPuff.jpg

You sir deserve a cookie. I havent laughed like that in a while.

[Deophaun]

http://i867.photobucket.com/albums/ab238/tomasdiaz/Salsa/HuffPuff.jpg
Apparently the wolf attempted to use an explosive rune between those frame and lost his left arm in the process.

[Ephemeral_Being]

As the rune explodes when you read it, destroying the page and thus the other 99 runes on it, what tower is taken down by 6d6 points of force damage?

Seriously? That's what would happen? I knew about the hazy distortion effect in the air from stacking them, but I figured you could super-impose a ton of them one line. And then read them all at once. Causing a 600d6 explosion.

I guess your interpretation makes more sense, though. I am going to have some unhappy players tomorrow night...

[Deophaun]

Seriously? That's what would happen? I knew about the hazy distortion effect in the air from stacking them, but I figured you could super-impose a ton of them one line. And then read them all at once. Causing a 600d6 explosion.

I guess your interpretation makes more sense, though. I am going to have some unhappy players tomorrow night...
If you try to read them, yes. It's a more open question of what happens if you dispel them, as the game doesn't say whether they are dispelled simultaneously or in series.

[Ephemeral_Being]

If you try to read them, yes. It's a more open question of what happens if you dispel them, as the game doesn't say whether they are dispelled simultaneously or in series.

Interesting. I shall inform my group thusly, and allow them to operate under the assumption that a failed dispel would cause them all to go off.

They thought this was a REALLY good plan. I'd hate for it to completely fail.

[Deophaun]

They thought this was a REALLY good plan. I'd hate for it to completely fail.
Here's a much more RAW solid way to do it:

Put your explosive runes on individual pages. Summon Monster a bunch of celestial monkeys. Give the pages to the monkeys, tell them to individually go over to the tower and (because they have an Int of 3) read the runes.

Now, with the dispel plan, keep in mind the idea is actually for the dispel to fail, because that's what triggers the explosion. So you want high CL explosive runes, and a minimal CL dispel. Furthermore, the person who made the runes cannot cast the dispel, because they automatically succeed on the check. As this is basically just being sprung on your players, feel free to retcon as necessary to fix, as their characters should have known about this (assuming anyone has a decent Spellcraft or Knowledge (arcana) score).

[tyckspoon]

Seriously? That's what would happen? I knew about the hazy distortion effect in the air from stacking them, but I figured you could super-impose a ton of them one line. And then read them all at once. Causing a 600d6 explosion.

I guess your interpretation makes more sense, though. I am going to have some unhappy players tomorrow night...

There are some tricks you can do that should trigger everything, but even if you rule it works remember that it's not a 600d6 blast - it's 100 6d6 blasts. Very relevant difference, especially when trying to destroy something with relevant resistances or Hardness; think about the difference between trying to break something by hitting it ten times with your bare hand and one good swing with a sledgehammer.

[Ephemeral_Being]

Here's a much more RAW solid way to do it:

Put your explosive runes on individual pages. Summon Monster a bunch of celestial monkeys. Give the pages to the monkeys, tell them to individually go over to the tower and (because they have an Int of 3) read the runes.

Now, with the dispel plan, keep in mind the idea is actually for the dispel to fail, because that's what triggers the explosion. So you want high CL explosive runes, and a minimal CL dispel. Furthermore, the person who made the runes cannot cast the dispel, because they automatically succeed on the check. As this is basically just being sprung on your players, feel free to retcon as necessary to fix, as their characters should have known about this (assuming anyone has a decent Spellcraft or Knowledge (arcana) score).

This is a new group of players. We're talking a month and a half of playing so far. This is the FIRST really creative scheme they've come up with. Instead of charging in swords flashing, or sneaking in through a window, they've put (relative to previous endeavors) a LOT of thought into this. Reading through the spell compendium, splat books, and (I'm guessing where they got the idea) Order of the Stick. As dumb as it may sound, I really want this plan to work. Because this is the kind of thing that makes Tabletop gaming so much better than anything on a Console. Coming up with an absurd solution to a problem, and just doing it.

So I'm not going to make them do the Monkey thing. I am going to make them figure out the Dispel part, though, through a combination of testing (which they were already planning on doing) and some Knowledge checks. Because that's fair. But the plan IS going to work. At least, in some fashion.

[Telok]

I don't know that it's a bad idea but it will be difficult. Physics is uniform, magic isn't. That is where you will have issues. Falling damage, normal fires, and seige weapons can all be figured and adjusted with some work. Getting the physics effects of spells will pretty much require a new calculation for each spell and some will be impossible without making many many assumptions.

Start with figuring out the physics effects of teleportation and which assumptions you need to make. Then try figuring out how much fire damage you need to boil water and how much cold damage you need to freeze water. Remember that there are multiple ways to get each effect, try to account for all of them or make a different rule for each one.